Conventionally, in a case where, for example, an oriented coating or the like is formed on a glass substrate such as a liquid crystal display, one practice has been to supply the glass substrate, on the surface of which a coating such as an oriented coating has been formed, to an exposure apparatus and to expose and thereby optically orient the oriented coating in a predetermined direction.
Such an exposure apparatus irradiates with an exposure light emitted from an exposure light source via a predetermined optical system, after the exposure light has been transmitted through a pattern of a light transmission region of a mask; the glass substrate to be exposed is placed on, for example, a movable stage, and the stage is moved to thereby convey the glass substrate to a region of irradiation with exposure light. Then, the practice has been to form a predetermined exposure region on the glass substrate by exposing the coating formed on the glass substrate, in correspondence with the pattern of the mask.
Thus, with a member to be exposed such as a glass substrate that is conveyed by a conveying apparatus such as a stage, the formation region of the oriented coating or the like is considerably affected by the positional accuracy of a conveying apparatus, the mask, and the like. As such, there has been proposed a variety of techniques for higher accuracy in exposing a predetermined region of a member to be exposed.
For example, Patent Document 1 discloses an apparatus for exposing a film; a pair of rectangular markings are added to two sides of the film, at film side parts on the outside of a region to be exposed. Then, the position of the mask is adjusted so that a predetermined region of the film is irradiated with the exposure light, by optically detecting the shape of the markings for alignment in a movement direction of the film as well as a direction perpendicular to the movement direction in a state where the conveyance of the film has been stopped.
The member to be exposed may be a film, in which case, for example, a pair of rollers 80, 81 as are illustrated in FIGS. 9 and 10 is used as a conveying apparatus for continuously conveying the film to the exposure apparatus. That is, as illustrated in FIGS. 9 and 10, a film 2 to be exposed is conveyed by being rolled up between each step until the film is processed from a film base material to a film that is the finished product. In the process of being supplied to the exposure apparatus, with a roll of the film mounted coaxially onto the supply-side roller 80, the film 2 is sequentially taken up from a leading end by the take-up-side roller 81. As illustrated in FIG. 9, the practice has been to use exposure light to continuously irradiate, for example, an oriented coating formed on the surface of the film, having been passed through the exposure apparatus, spanning from the supply-side roller 80 to the take-up-side roller 81, thus exposing a predetermined exposure region of the film along the movement direction of the film. This format is called a roll-to-roll format.
In a case where a film is exposed in a roll-to-roll format, the film 2 may in some cases meander in a direction perpendicular to the movement direction while the film 2 is being fed from the supply-side roller 80 toward the take-up-side roller 81, as illustrated in FIG. 10, due to, for example, the spacing between the roll of film and the rollers 80, 81 of the conveying apparatus, an error in take-up of the film into the roll, or the like, and a problem has emerged in that this causes a decline in the exposure accuracy for the film 2.
There have accordingly been proposed a variety of techniques for correcting the meandering of the film, as is disclosed in, for example, Patent Documents 2 and 3. The technique disclosed in Patent Document 2 is one where a detector for detecting an edge position of a web such as a film is provided and, depending on the detection result of the detector, the supply-side roller is moved in the axial direction by a cylinder or the like to correct for meandering of the web in a direction perpendicular to the movement direction.
Patent Document 3 discloses a technique where, in a case where a long work piece such as a film is exposed in two separate cycles, then during the first cycle of exposure, a pattern is formed on the work piece and markings for alignment are added intermittently at equal intervals of a predetermined pattern length, and during the second cycle of exposure, the positional deviation and incline of the work piece are detected by imaging the alignment marks and the mask position and incline are corrected.
FIG. 11 is a drawing illustrating by way of example a conventional exposure apparatus of a model where exposure light sources 11 for emitting an exposure light are arranged so as to be face-to-face in increments of pairs each corresponding to one mask 12, and irradiate with the exposure light from mutually different directions. An exposure apparatus of such a model is used, for example, to expose an oriented material coating in the process of forming an oriented coating on a glass substrate such as a liquid crystal display or on a film base material such as a polarizing film. That is, in a case where an oriented coating is formed by exposure using the exposure apparatus, the practice is to supply to the exposure apparatus a member to be exposed on the surface of which an oriented material coating has been formed and respectively irradiate predetermined regions from different directions with the exposure light to form an oriented coating that has been oriented in different directions. According to the exposure apparatus of such description, it would be possible to, for example, segment a region of the film corresponding to one picture element into two in the width direction thereof, or to respectively segment the film in the width direction thereof into regions corresponding to a pixel, and form an oriented coating with different orientation directions respectively in each of the segmented regions. This feature of the orientation direction of the oriented coating causes the liquid crystal molecules sandwiched between glass substrates to behave differently when a voltage is applied, depending on the orientation direction of the oriented coating, and this makes it possible to broaden the angle of view of a display apparatus and moreover makes it possible to use the film thus produced also as a polarizing film for a three-dimensional (3D) display or the like; there has been growing focus of late on such techniques of film exposure.
When a film is exposed by such an exposure apparatus, the film is susceptible to suffering undulation while being conveyed, and a problem has emerged in that this causes a deviation in the exposure position. In order to reduce the impact of this deviation in exposure position, one practice of exposure with, for example, an exposure apparatus where a plurality of light sources is arranged side by side in the movement direction of the film as described above has been to not to use one mask in exposure but rather to use a plurality of masks 12, as illustrated in, for example, FIGS. 11 and 12, where each of the masks 12 is arranged in a staggered fashion so as to be side by side in the direction of movement of the member to be exposed and the width direction perpendicular thereto, and a exposure light source 11 is provided for each of the masks. Exposed light from the exposure light sources is then transmitted through masks 121 to 124 and, as illustrated in FIG. 12, on an upstream side from which the film is being supplied, the film 2 is exposed at exposure regions A and C by the masks 121 and 122, which are arranged spaced apart from each other, while on the downstream side a region B between the exposure regions A and C is exposed by the mask 123 and a region D adjacent to the exposure region C is exposed by the mask 124. This makes it possible to form at high accuracy a pattern of segmented orientation on substantially the full surface of the film 2.